The present invention relates to an electromagnetic induction heater device, which is sometimes called a ceramics hob and is used as an induction burner.
A prior induction heater or an induction burner is shown in FIG. 1, in which the numeral 1 is a flat coil support made of heat-resisting insulation material, 2 is a coil mounted on said coil support 1, 3 is a housing, 4 is a heat-resisting insulation cover plate, and 5 is a load which is for instance a pan for cooking. The coil 2 is made of a litz wire.
When the coil 2 is energized by high frequency power (for instance, 20-40 kHz), the load 5 is heated by eddy current loss and/or induction loss of electromagnetic flux field generated by the coil 2.
However, a prior induction burner has the disadvantage as follows.
Since the coil support 1 is made of heat-resisting insulation material, the electromagnetic field generated by the coil 2 leaks behind the support 1. The leakage flux is even as high as the effective front field. As some electronic devices, like a high frequency power source (not shown), is mounted in the housing, that device is also heated by the flux by the coil 2 itself.